HARO is a free daily email service that connects journalists with sources. The 800,000-plus people who use it receive three e-mails a day loaded with queries from journalists who describe what they’re looking for in a source and why.

If you make the effort to scan those emails for opportunities to contribute your expertise or experience, you and your book could be mentioned in the news or on a blog.

The trick to getting an interview and subsequent exposure — all of which you don’t pay for — is responding to the right queries appropriately. More on that later, though. It helps to first understand more about HARO and how the system works.